The present invention relates to a method of making liquid crystal display (LCD), and more specifically, to a method of forming a LCD with a wide viewing angle.
Recently, personal data assistant (PDA) and notebook are remarkably progressing. The demanded requirements of the displays for portable use are light weight and low power consumption. Thin film transistor-liquid crystal display (TFT-LCD) can meet the above requirements and is known as the display required for the high pixel density and quality. In general, the TFT-LCD includes a bottom plate formed with thin film transistors and pixel electrodes and a top plate formed with color filters. The liquid crystal is filled between the top plate and the bottom plate. In each unit pixel, a capacitor and a further capacitor are provided which are formed by virtue of the TFT serving as the switching element of the unit pixel. When the data voltage is applied to the TFT, the arrangement of the liquid crystal molecules is change, thereby changing the optical properties and displaying the image.
In general, the viewing angle and the color performance are very important issues for the design of the LCD. A color filter (CF) plate is used in the LCD to show the colored portion of the screen. One of the trends for the LCD technology is to improve the viewing angle of the LCD. However, the viewing angle and contrast ratio of LCD are still insufficiently applied to products having large screen. One of an article relating to a vertical-alignment-mode LCD can be seen in SID""97 DIGEST p845xcx9cp848, proposed by K. Ohmuro, S. Kataoka, T. Sasaki and Y. Koike. In the reference, the VA-LCD (vertically aligned LCD) has been implemented by optimizing a vertically aligned mode with a domain-divided structure and an optical compensator. This vertical-alignment-mode LCD has a wide viewing angle over 70xc2x0, a fast response ( less than 25 ms), and a high contrast ratio of over 300. However, it still suffers some drawbacks. For example, the formation of the two-domain structure needs the mask rubbing process, which is complicated and expensive. The rubbing process also produces ESD (Electrostatic Discharge) problem and particles. In addition, the mask rubbing will lead to a result of image sticking.
An object of the present invention is to provide a method of forming a LCD with wide viewing angle.
Another object of the present invention is to form a bump structure in LCD cell, thereby increasing the pre-titled angle of the liquid crystal molecules.
The present invention includes a pair of light polarizers consisting of a polarizer and an analyzer. An upper transparent insulating substrate is formed under the polarizer. A compensator is formed on the analyzer. A bump structure is formed above the lower substrate. The liquid crystal molecules have larger pre-titled angle that are formed on the bump structure having predetermined lending directions. The method of forming the bump structure is seen as follows.
The method uses one photomask and one-exposure steps wherein said photomask comprising two major portions that are formed by mirror image with each other, the wides of openings formed in said photomask being increased from a central portion to an edge portion, the spaces between two adjacent said openings being decreased from said central portion to said edge. Then, shift said substrate with a distance to a direction perpendicular to a surface of said photomask. Next, expose said photosensitive material layer by using said photomask; and developing the photosensitive material to form said bump structure.